New York (CNN) -- There are some experiences that are too painful to bear. For New York Fire Chief Stephen King that event is 9/11.

So painful were the memories of September 11, 2001, King retired from the fire department, and avoided bridges and tunnels.

At one point, the native New Yorker stopped coming to Manhattan altogether.

"I was in the north tower, the one that got hit first. Where I was and what I saw that day -- the many people that jumped, the magnitude of it -- was just overwhelming," he told CNN.

But thanks largely to a new tool in trauma treatment -- virtual reality -- King has returned to face the past.

"When I see the plane hit, the smoke come out, it brings me back there," he said.

Using video game technology, therapists create programs that mimic the traumatic event.

Dr. JoAnn Difede, an associate professor for the department of psychiatry and the director of Anxiety and Traumatic Stress Studies Program at Weill Cornell Medical College, is working with World Trade Center survivors to help them overcome the trauma.

"The idea behind the treatment is to systematically expose the patient to aspects of their experience in a graded fashion so they can confront their fear of the trauma," she told CNN.

The program is basic compared to slick video games on the market, but the developers say the simplicity allows patients to fill in the blanks.

The treatment gives patients the ability to reconnect with their memories of that day, an important step for the healing process, Difede said.

It can take weeks for a patient to advance just one stage, but Difede said she had been pleasantly surprised by the results.

"Our patients have done very well. They tend to get better more quickly and it seems to engage them emotionally that allows more of their memories to be recalled," she said.

The 3D imaging software has been created by Atlanta-based company Virtually Better. Initial studies have been so convincing that the U.S. Army has asked Virtually Better to create a program to help soldiers returning from Iraq.

The company is also developing programs to help manage pain and treat addictions.

Difede said that while results had been promising, the treatment was not a magic elixir and there was still a lot to learn about the virtual reality therapies.